Implement support for using functions in custom attributes

refs Icinga#7564

doc/3-monitoring-basics.md

@@ -1732,6 +1732,7 @@ There are several ways of using custom attributes with [apply rules](3-monitorin
 [boolean](15-language-reference.md#boolean-literals)) for expression conditions (`assign where`, `ignore where`)
 * As [array](15-language-reference.md#array) or [dictionary](15-language-reference.md#dictionary) attribute with nested values
 (e.g. dictionaries in dictionaries) in [apply for](3-monitoring-basics.md#using-apply-for) rules.
+* As a [function object](#functions)
 
 Features like [DB IDO](3-monitoring-basics.md#db-ido), Livestatus(#setting-up-livestatus) or StatusData(#status-data)
 dump this column as encoded JSON string, and set `is_json` resp. `cv_is_json` to `1`.

lib/icinga/macroprocessor.cpp

@@ -25,6 +25,7 @@
 #include "base/logger.hpp"
 #include "base/context.hpp"
 #include "base/dynamicobject.hpp"
+#include "base/scriptframe.hpp"
 #include <boost/foreach.hpp>
 #include <boost/algorithm/string/split.hpp>
 #include <boost/algorithm/string/join.hpp>
@@ -166,6 +167,8 @@ Value MacroProcessor::InternalResolveMacros(const String& str, const ResolverLis
 	size_t offset, pos_first, pos_second;
 	offset = 0;
 
+	Dictionary::Ptr resolvers_this;
+
 	String result = str;
 	while ((pos_first = result.FindFirstOf("$", offset)) != String::NPos) {
 		pos_second = result.FindFirstOf("$", pos_first + 1);
@@ -194,6 +197,22 @@ Value MacroProcessor::InternalResolveMacros(const String& str, const ResolverLis
 			found = true;
 		}
 
+		if (resolved_macro.IsObjectType<Function>()) {
+			Function::Ptr func = resolved_macro;
+
+			if (!resolvers_this) {
+				resolvers_this = new Dictionary();
+
+				BOOST_FOREACH(const ResolverSpec& resolver, resolvers) {
+					resolvers_this->Set(resolver.first, resolver.second);
+				}
+			}
+
+			ScriptFrame frame(resolvers_this);
+			std::vector<Value> args;
+			resolved_macro = func->Invoke(args);
+		}
+
 		if (!found) {
 			if (!missingMacro)
 				Log(LogWarning, "MacroProcessor")